1. Field of the Invention
The present invention relates to a variable magnification copying apparatus which utilizes a plurality of imaging element arrays.
2. Description of the Prior Art
There is known an imaging element array including a plurality of small diameter rod-like light guiding elements with its progressive reduction of refractive index in the radial direction thereof and with an imaging function, available from Nippon Sheet Glass Co., Ltd. as SELFOC (trade mark), these light guiding elements being arranged in one or more lines to form a composite image consisting of plural small image sections of an original. In recent years, an imaging element array for forming the image of an original at various magnifications other than real size has been proposed, for example, in Japanese Laid-open Patent Application No. 56-24308 or U.S. Pat. No. 4,405,207. Furthermore, a magnification changeable system wherein plural imaging element arrays are used has been proposed, for example, in U.S. Pat. Nos. 4,331,380 or 4,394,083.
If such a variable magnification copying system is of a structure in which the imaging element arrays having different magnifications are changed in position upon the change of magnification, a highly precise array moving mechanism will be required to always obtain a properly focused image at any magnification since each of these imaging element arrays normally has a relatively small focal depth in the order of 0.1 to 0.7 mm. It is thus preferred that the respective imaging element arrays remain stationary while at the same time a mechanism for changing the optical path, such as a shutter or the like, is used to prevent out-of-focus image. In such a case, however, a position at which the photosensitive member is to be exposed to the light image of the original varies in accordance with the selected magnification. When the magnification is changed, therefore, the positional relationship between the image of the original and the transfer material will be disturbed.
U.S. Pat. Nos. 3,865,482 and 4,126,389 disclose systems for changing the magnification while at the same time varying the timing with which transfer materials are fed out. However, these systems are adapted to change the magnification by moving a large-sized lens structure such that the exposure position of the photosensitive member to the image of an original is not changed in the direction in which the photosensitive member is moved. The just above mentioned U.S. patents do not suggest the conveying and controlling technique of transfer material which can be used in a variable magnification copying system which utilizes a plurality of imaging element arrays having different imaging magnifications and is of such a structure that the exposure position of the light original image through the imaging element array is changed in the direction of the photosensitive member's movement.